arXiv subjects

Debabrata Mondal

Publications and source records attributed to Debabrata Mondal.

11 recordsLinked to original sources

arXiv2026

Chaos to Synchronization and Dissipative Quantum Scarring in Open Coupled top-Dicke model in a Lossy Cavity

We present a variant of the Dicke model, termed as the open coupled-top Dicke model, which enables the exploration of rich non-equilibrium phenomena, particularly the fate of quantum scars in an open environment. This model can effectively be realized by coupling a two-species Bose-Josephson junction to a lossy cavity. Photon loss induces spontaneous synchronization via projection onto a dissipation-free subspace, along with transient chaos followed by restoration of synchronization and coherence. We identify two distinct scarring phenomena in the presence of dissipation. One remains protected, exhibiting persistent revivals, while the scar associated with the superradiant phase displays a dissipation-induced slow decay of the survival probability. Remarkably, for sufficiently small spin magnitude, the chaos-assisted macroscopic quantum tunneling is linked to the latter type of scarring. The results can be readily tested in ongoing cavity QED experiments and have broader applicability in other platforms.

quant-ph↗

arXiv2026

Dissipation as a Resource: Synchronization, Coherence Recovery, and Chaos Control

Dissipation is commonly regarded as an obstacle to quantum control, as it induces decoherence and irreversibility. Here we demonstrate that dissipation can instead be exploited as a resource to reshape the dynamics of interacting quantum systems. Using an experimentally realizable Bose-Josephson junction containing two bosonic species, we demonstrate that dissipation enables distinct dynamical behaviors: synchronized phase-locked oscillations, transient chaos with long-time coherence recovery, and steady-state chaos. The emergence of each behavior is determined by experimentally tunable parameters. At weak interactions, the two components synchronize despite dissipation, exhibiting long-lived coherent oscillations reminiscent of a boundary time crystal. Stronger interactions induce a dissipative phase transition into a self-trapped regime accompanied by chaotic dynamics. Remarkably, dissipation regulates the lifetime of chaos and enables the recovery of coherence at long times. By introducing a controlled tilt between the wells, transient chaos can be converted into persistent steady-state chaos. We further show that standard spectral diagnostics fail to distinguish between the two chaotic regimes, revealing that spectral statistics primarily reflect short-time instability. These results establish dissipation as a powerful tool for engineering dynamical phases, restoring quantum coherence, and controlling the duration of chaotic behavior and information scrambling.

quant-ph↗

arXiv2026

Transient and steady-state chaos in dissipative quantum systems

Dissipative quantum chaos plays a central role in the characterization and control of information scrambling, non-unitary evolution, and thermalization, but it still lacks a precise definition. The Grobe-Haake-Sommers conjecture, which links Ginibre level repulsion to classical chaotic dynamics, was recently shown to fail [Phys. Rev. Lett. 133, 240404 (2024)]. We properly restore the quantum-classical correspondence through a dynamical approach based on entanglement entropy and out-of-time-order correlators (OTOCs), which reveal signatures of chaos beyond spectral statistics. Focusing on the open anisotropic Dicke model, we identify two distinct regimes: transient chaos, marked by rapid early-time growth of entanglement and OTOCs followed by low saturation values, and steady-state chaos, characterized by high long-time values. We introduce a random matrix toy model and show that Ginibre spectral statistics signals short-time chaos rather than steady-state chaos. Our results establish entanglement dynamics and OTOCs as reliable diagnostics of dissipative quantum chaos across different timescales.

quant-ph↗

arXiv2025

Dissipative chaos and steady state of open Tavis-Cummings dimer

We consider a coupled atom-photon system described by the Tavis-Cummings dimer (two coupled cavities) in the presence of photon loss and atomic pumping, to investigate the quantum signature of dissipative chaos. The appropriate classical limit of the model allows us to obtain a phase diagram identifying different dynamical phases, especially the onset of chaos. Both classically and quantum mechanically, we demonstrate the emergence of a steady state in the chaotic regime and analyze its properties. The interplay between quantum fluctuation and chaos leads to enhanced mixing dynamics and dephasing, resulting in the formation of an incoherent photonic fluid. The steady state exhibits an intriguing phenomenon of subsystem thermalization even outside the chaotic regime; however, its effective temperature increases with the degree of chaos. Moreover, the statistical properties of the steady state show a close connection with the random matrix theory. Finally, we discuss the experimental relevance of our findings, which can be tested in cavity and circuit quantum electrodynamics setups.

cond-mat.quant-gas↗

arXiv2025

Self-trapping phenomenon, multistability and chaos in open anisotropic Dicke dimer

We investigate semiclassical dynamics of a coupled atom-photon interacting system described by a dimer of anisotropic Dicke model in the presence of photon loss, exhibiting a rich variety of non-linear dynamics. Based on symmetries and dynamical classification, we characterize and chart out various dynamical phases in a phase diagram. A key feature of this system is the multistability of different dynamical states, particularly the coexistence of various superradiant phases as well as limit cycles. Remarkably, this dimer system manifests self-trapping phenomena, resulting in a photon population imbalance between the cavities. Such a self-trapped state arises from a saddle-node bifurcation, which can be understood from an equivalent Landau-Ginzburg description. Additionally, we identify a unique class of oscillatory dynamics self-trapped limit cycle, hosting self-trapping of photons. The absence of stable dynamical phases leads to the onset of chaos, which is diagnosed using the saturation value of the decorrelator dynamics. Moreover, the self-trapped states can coexist with chaotic attractor, which may have intriguing consequences in quantum dynamics. Finally, we discuss the experimental relevance of our findings, which can be tested in cavity and circuit quantum electrodynamics setups.

cond-mat.quant-gas↗

arXiv2024

Emergence of a quasi-ergodic steady state in a dissipative Tavis-Cummings array

In an atom-photon interacting system described by Tavis Cummings Hubbard (TCH) model, we demonstrate the emergence of a quasi-steady state in a dissipative environment that exhibits intriguing ergodic behavior. The TCH model undergoes a dissipative transition from normal to superradiant phase hosting a gapped Higgs and gapless Goldstone modes. However, in a large region of the phase diagram, the instability of the Goldstone mode leads to the disappearance of the stable superradiant phase. In this regime, the decorrelator dynamics reveals light cone spreading of the perturbations and positive Lyapunov exponent, indicating enhanced fluctuations. Remarkably, a quasi-steady state emerges under quench dynamics in this unstable regime; in this state, a class of collective quantities such as site averaged photon number and atomic excitations approach a steady value, in spite of large temporal fluctuations in corresponding microscopic variables. This quasi-steady state describes an incoherent fluid of photons with significant phase fluctuation. The phase space dynamics reveals a fascinating ergodic behavior in presence of dissipation, leading to the characterization of the dynamical variables into two distinct classes. The first class includes site-averaged photon numbers and atomic excitations; these exhibit a stationary distribution regardless of the initial condition indicating ergodic behavior. The second class of variables, particularly those related to phase in contrast, retain information about the initial conditions, resulting in a violation of ergodicity for finite size system. Additionally, the dynamical variables of the ergodic class exhibit fascinating collective scarring phenomenon as the peak of their distribution is attracted towards the unstable steady state, analogous to the single particle quantum scar. We discuss the relevance of our findings in the current experiments.

cond-mat.stat-mech↗

arXiv2024

Nonequilibrium dynamics of the Jaynes-Cummings dimer

We investigate the nonequilibrium dynamics of a Josephson-coupled Jaynes-Cummings dimer in the presence of Kerr nonlinearity, which can be realized in the cavity and circuit quantum electrodynamics systems. The semiclassical dynamics is analyzed systematically to chart out a variety of photonic Josephson oscillations and their regime of stability. Different types of transitions between the dynamical states lead to the self-trapping phenomenon, which results in photon population imbalance between the two cavities. We also study the dynamics quantum mechanically to identify characteristic features of different steady states and to explore fascinating quantum effects, such as spin dephasing, phase fluctuation, and revival phenomena of the photon field, as well as the entanglement of spin qubits. For a particular "self-trapped" state, the mutual information between the atomic qubits exhibits a direct correlation with the photon population imbalance, which is promising for generating photon mediated entanglement between two non interacting qubits in a controlled manner. Under a sudden quench from stable to unstable regime, the photon distribution exhibits phase space mixing with a rapid loss of coherence, resembling a thermal state. Finally, we discuss the relevance of the new results in experiments, which can have applications in quantum information processing and quantum technologies.

quant-ph↗

arXiv2022

Classical route to ergodicity and scarring phenomena in a two-component Bose-Josephson junction

We consider a Bose-Josephson junction (BJJ) formed by a binary mixture of ultracold atoms to investigate the manifestation of coherent collective dynamics on ergodicity and quantum scars, unfolding the connection between them. By tuning the inter- and intra-species interaction, we demonstrate a rich variety of Josephson dynamics and transitions between them, which plays a crucial role in controlling the overall ergodic behavior. The signature of underlying classicality is revealed from the entanglement spectrum, which also elucidates the formation of quantum scars of unstable steady states and of periodic orbits leading to athermal behavior. The degree of ergodicity across the energy band and scarring phenomena can be probed from the auto-correlation function as well from the phase fluctuation of the condensates, which has relevance in cold atom experiments.

cond-mat.stat-mech↗

arXiv2022

Quantum transitions, ergodicity, and quantum scars in the coupled top model

We consider an interacting collective spin model known as coupled top (CT), exhibiting a rich variety of phenomena related to quantum transitions, ergodicity, and formation of quantum scars, discussed in [Phys. Rev. E 102, 020101(R) (2020)]. In this work, we present a detailed analysis of the different type of transitions in CT model, and find their connection with the underlying collective spin dynamics. Apart from the quantum scarring phenomena, we also identify another source of deviation from ergodicity due to the presence of non-ergodic multifractal states. The degree of ergodicity of the eigenstates across the energy band is quantified from the relative entanglement entropy as well as multifractal dimensions, which can be probed from non-equilibrium dynamics. Finally, we discuss the detection of non-ergodic behavior and different types of quantum scars using `out-of-time-order correlators', which has relevance in the recent experiments.

cond-mat.stat-mech↗

arXiv2021

Dynamical route to ergodicity and quantum scarring in kicked coupled top

Unlike classical system, understanding ergodicity from phase space mixing remains unclear for interacting quantum systems due to the absence of phase space trajectories. By considering an interacting spin model known as kicked coupled top, we elucidate the manifestation of phase space dynamics on local ergodic behavior of its quantum counterpart and quantum scarring phenomena. A transition to chaos occurs by increasing the kicking strength, and in the mixed phase space, the islands of regular motions within the chaotic sea clearly exhibit deviation from ergodicity, which we quantify from entanglement entropy and survival probability. Interestingly, the reminiscence of unstable orbits and fixed points can be identified as scars in quantum states, exhibiting athermal behavior and violation of Berry's conjecture for ergodic states. We also discuss the detection of quantum scars by a newly developed method of 'out-of-time-order correlators', which has experimental relevance.

cond-mat.stat-mech↗

arXiv2020

Chaos and quantum scars in a coupled top model

We consider a coupled top model describing two interacting large spins, which is studied semiclassically as well as quantum mechanically. This model exhibits variety of interesting phenomena such as quantum phase transition (QPT), dynamical transition and excited state quantum phase transitions above a critical coupling strength. Both classical dynamics and entanglement entropy reveals ergodic behavior at the center of energy density band for an intermediate range of coupling strength above QPT, where the level spacing distribution changes from Poissonian to Wigner-Dyson statistics. Interestingly, in this model we identify quantum scars as reminiscence of unstable collective dynamics even in presence of interaction. Statistical properties of such scarred states deviate from ergodic limit corresponding to random matrix theory and violate Berry's conjecture. In contrast to ergodic evolution, oscillatory behavior in dynamics of unequal time commutator and survival probability is observed as dynamical signature of quantum scar, which can be relevant for its detection.

cond-mat.quant-gas↗